Earth's Crust in Motion

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Vocabulary
Earthquake- the shaking and trembling that results from the movement of rock beneath Earth's surface.
Stress- a force that acts on rock to change its shape or volume.
Shearing- stress that pushes a mass of rock in two opposite directions.
Tension- a force that stretches rock to make it thinner.
Compression- a force that squeezes rocks until it folds or breaks.
Deformation- any change in the volume or shape of Earth's crust.
Fault- a break in Earth's crust where slabs or crust slip past each other.
Strike-slip Faults- a fault where rocks slip past each other sideways with little up-or-down motion.
Normal Faults- a fault that has a hanging wall and footwall that slides downwards.
Reverse faults- the exact opposite of a normal fault, which has a footwall and a hanging wall except sliding upwards.
Friction- the force that opposes the motion of one surface as it moves across another surface.
Fault-block Mountain- normal faults uplifting a block of rock.
folds- bends in rock that form when compression shortens and thickens part of Earth's crust.
Anticline- the fold in rock that bends upward into an arch.
Syncline- a fold in rock that bends downward in the middle to form a bowl.
Plateau- a large area of flat land elevated high above sea level.

Outline

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Stress in the Crust

• Stress
  • the force that changes the shape and volume of rock
    • adds energy to rock

Types of Stress

• shearing
  • slip and breaks rock

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* tension

• pulls on crust
  • stretches rock, so it becomes thinner in the middle
• compression
  • squeezes rock till folds or breaks
    • like a giant trash compactor
• deformation
  • changes in the earth's crust

Kinds of Faults

• faults
  • a break in earth's crust
    • faults occur near boundaries

Strike-Slip Fault

• shearing
  • causes strike-slip fault
• boundaries form
  • called transform boundary
  • 

Normal Faults

• tension
  • causes normal faults
    • rock slips
    • fault that lies above is hanging wall
    • fault that lies below is footwall

Reverse Faults

• compression
  • causes reverse faults
    • reverse faults produce part of Appalachian Mountain

Friction Along Faults

• Friction
  • a force that opposes the motion of one surface as it moves across another surface
• Faults sometimes jam together because of friction
  • they will jerk free, which produces small earthquakes
    • stress is strong enough to overcome friction force

Mountain Building

• forces of plates can build up earth's surface

Mountains formed by Faulting

• Fault block mountain
  • forms when faults uplift a block of rock
    • Sierra Nevada of California is a fault-block mountain
    • Great Basin also has many ranges of fault block mountain
• two plates move away from each other
  • creates many normal faults

Mountains formed by Folding

• Folds
  • plate movement causes crust to fold
  • bends in rock that form compression
• California's northern Coast Range are partly the result of folding

Anticlines and Synclines

• A fold in rock that bends upward into an arch is Anticline
  • anticline is the Black Hills
  • Black Hill formed about 65 million years ago
• A fold in rock that bends downwards into an arch is Syncline
  • syncline can be as large as Illinois
  • The Illinois Basin is a syncline that stretches very far

Plateaus

• plateaus
  • the force that raises mountains
  • a large area of flat land above sea level
  • a lot of plateau lies more than 1500 meters above sea level

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